1. obliged, indebted. Grateful,thankful describe an appreciative attitude for what one has received. Grateful indicates a warm or deep appreciation of personal kindness as shown to one: grateful for favors; grateful to one's neighbors for help in time of trouble.Thankful indicates a disposition to express gratitude by giving thanks, as to a benefactor or to a merciful Providence; there is often a sense of deliverance as well as of appreciation: thankful that one's life was spared in an accident; thankful for the comfort of one's general situation.3. pleasant, gratifying, satisfying.

1550s, "pleasing to the mind," also "full of gratitude," from obsolete adj. grate "agreeable, thankful," from Latin gratus "pleasing" (see grace). "A most unusual formation" [Weekley]. Hard to think of another case where English uses -ful to make an adjective from an adjective. Related: Gratefully; gratefulness.